Meeting Abstract

12.4  Jan. 4  Light habitats and the role of polarized iridescence in the sensory ecology of neotropical nymphalid butterflies (Lepidoptera: Nymphalidae) DOUGLAS, J. M.*; CRONIN, T. W.; CHIOU, T. H.; DOMINY, N. J.; RUTOWSKI, R. L.; Arizona State University; University of Maryland, Baltimore County; University of Maryland, Baltimore County; University of California, Santa Cruz; Arizona State University jondouglas@asu.edu

Recent hypotheses suggest the detection and exploitation of polarized light in a signaling context may have adaptive value in forest habitats, where illumination varies greatly in spectrum and intensity. Here we test whether polarized iridescence and forest light habitats are evolutionarily correlated by investigating the extent to which neotropical lepidoptera exhibit polarized iridescence, and evaluating the types of habitats in which polarization tends to be found. We limited our examination to species belonging to the Nymphalidae found within Costa Rica. Polarized specimens were distinguished using a polarizing filter and images indicating the degree of polarization with a color coding system. Adult flight habits and associated light environments were obtained from the literature. A significant correlation (Yates Chi² = 40.177; d.f. = 1; P < 0.0001) was found between polarized reflectance patterns of butterfly wings and forest light habitats. We then constructed a phylogeny of the Nymphalidae from the literature and performed a phylogenetic concentrated changes test, with the Papilionidae as an outgroup (Maddison, 1990). This test shows robust support for the correlated evolution of polarized reflectance patterns with life in forest environments suggesting a strong selective force on the wing patterns forest butterflies. These results are consistent with the hypothesis that the utilization and detection of polarized light has adaptive ecological value in forest habitats having complex ambient light conditions.